Project 1 Mechanical design of battery pack
Battery pack capacity: 18 kWh
Cell: ANR26650M1-B
Prepare a detailed battery pack drawing along with its enclosure. State your assumptions.
Answer:
The cell model is ANR26650M1-B datasheet is shown below.
Some of the specifications are listed below as per the datasheet:
- Nominal voltage: 3.3 V
- Nominal capacity: 2.5 Ah
- Nominal energy: 8.25 Wh
- Specific power: 2600 W/kg
- Internal Impedance (1kHz AC typical): 6 mΩ
- Maximum Continuous Discharge: 50A
- Maximum Pulse Discharge (10 seconds): 120A
- Operating Temperature: -30°C to 55°C
- Recommended Std Charge Method: 2.5A
- Recommended Fast Charge Method to 80% SOC: 10A
- Cell Dimensions : 26 x 65 mm (dia x length)
- Cell Weight: 76g
Calculations are carried out based on the battery pack capacity: 18 kWh
Cell energy = Nominal voltage x Nominal capacity
= 3.3 x 2.5
= 8.25 Wh
Cell volume = pi * (r^2) * h
= 3.145 x (0.013^2) x 0.065
= 0.03451 m^3
Volumetric energy(Wh/m^3) = Cell energy / Cell volume
= 8.25 / 0.03451
= 239.061 Wh/m^3
Gravimetric energy(Wh/kg) = Cell energy / Cell Weight
= 8.25 / 0.076
= 108.552 Wh/kg
Batter pack calculation:
Assuming the vehicle range = 200 km, and nominal voltage in series = 200 V(depends on the moter ratings)
Avg. energy required per kilometer(Wh/km) = 18000/200
= 90 wh/km
Number of cells in series = nominal voltage in series / nominal cell voltage
= 200 / 3.3
= 60.6 = 61 cells
Battery pack capacity = Battery pack energy / nominal voltage in series
= 18000 / 200
= 90 Ah
Number of cells in parallel = Battery pack capacity / nominal cell capacity
= 90 / 2.56
= 35.15 = 36 cells
So the battery pack combination will be 36P61S
Therefore, the total number of cells in a battery pack = 36 x 61
= 2196 cells
Battery pack:
Battery pack mass = total number of cells in a battery pack * Cell Weight
= 2196 x 0.076
= 166.896 kg
Length of the battery pack = Number of cells in series * cell diameter
= 61 x 0.026
= 1.586 m
Width of the battery pack = number of cells in parallel * cell diameter
= 36 x 0.026
= 0.936 m
Battery pack area = Length of the battery pack * Width of the battery pack
= 1.586 x 0.936
= 1.484 sq.m
Components required for battery pack construction are Cells, nickel strips, cell holder, spot welder, solder, and PVC heat sink film.
Step 1: Arrange the cell holders in 36 by 61
Step 2: Arrange all the cells in the cell holder and cover these cells with another cell holder from the top.
Step 3: Connect the cells with the nickel strip & spot welding process. Make the cell configuration by series & parallel combination.
Step 4: Connect the heat sink to the battery pack
Step 5: Then connect BMS to the battery
Step 6: At last place the battery pack inside the casing known as the battery enclosure.
